Linksys router ripe for remote takeover

Stealth attack exploits gullible management console

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A security researcher has discovered a flaw in a popular Linksys router that could allow attackers to remotely hijack the device using its web management console.

The Linksys WAG54G2 fails to properly inspect addresses typed in to browsers accessing the management console, allowing attackers to inject powerful shell commands into the router's Linux operating system, researcher Michal Sajdak warns here. The flaw is trivial to exploit when users fail to change the administrative password that's used by default.

"When you are logged in to the web administration, simple injection leads to OS root access," Sajdak writes. "It can be exploited using CSRF and these credentials (assuming a user did not change default user/password). One can still backdoor the router having access to web administration. Another outcome of the bug is an [ability] to quite easily examine what services are running on the router, what is its internal configuration, etc."

Representatives from Cisco, which owns Linksys, didn't respond to a request for comment by time of publication.

The web management console is turned on by default for users on the router's local area network, so the attack seems easiest for unauthorized people who already have access to the network. But using a technique known as CSRF, or cross-site request forgery, remote takeover of the device is also possible.

Sajdak says he notified Cisco of the vulnerability in March but as of Sunday there still was no fix. Users of the device are strongly urged to change the default password, a piece of advice that has fallen on deaf ears in the past.

Update

Web application expert Russ McRee of HolisticInfoSec.org, emailed to say the vulnerability is almost identical to one he found in a separate Linksys router. "When I contacted Linksys regarding a CSRF issue in the WRT160N I was advised that they wouldn't fix it," he wrote.